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Product Safety Overview

Making a product safe requires an understanding of the hazards that exist in each electrical product. Certain potential hazards are inherent in all electrical products because of the manner in which they are powered and how they perform their intended functions. Even though a product requires an electrical power source and uses electrical or electronic components, it should not present an electrical shock hazard to the user. Four fundamental hazards must be evaluated as part of any product safety evaluation:

Specifications that address these hazards are contained in every product safety standard. Although additional safety requirements are also included in most safety standards, these four hazards are the foundation upon which all safety standards are based. This guide is only concerned with electrical safety testing methods. It focuses only on the tests and equipment needed to minimize electrical shock and does not discuss mechanical/physical injury and fire hazards.

Electrical Shock

Electrical shock and its effects can be caused and influenced by several factors. The primary effect is the result of electrical current passing through the human body. Severity of the injury to the human body is directly affected by such variables as: the nature of the electrical voltage (AC vs. DC); the pathway through the human body; conductivity of the contact (wet or dry); the size and shape of the individual involved (i.e.,the person’s impedance), duration of the contact, and the size of the contact area. All these affect the magnitude of current that flows through the person’s body.

It is difficult to set standards that protect users from all possible fault conditions, but many requirements have been established to provide fundamental levels of user safety. The previous example is the reason GFCI (ground fault current interrupters) are required by the National Electrical Code in wet locations. Such devices automatically interrupt power when a ground current larger than 5 mA exists for more than a few milliseconds. These devices have saved countless people from being electrocuted in their own homes. The frequency in Hertz (Hz); i.e, cycles per second, of the electrical source is also a determining factor in the subsequent effect and/or reaction of the human body when subjected to electrical current flow. Studies have shown that low frequency voltages, such as AC power line voltage (50/60Hz) which is commonly found in the household or workplace, have a more immediate and damaging effect than DC voltage when contact with the human body occurs. Therefore, it is important that electrical products and appliances be designed to protect the user from contact with AC line/primary voltage.

Most safety standards address this issue by incorporating requirements that mandate appropriate product enclosures: connectors that do not allow direct user access, good dielectric or insulating barriers, as well as very low leakage current. Not all voltage potentials, however, are considered hazardous. Some are considered safe for user contact because of the low levels at which they operate. Since the standards are very specific about these limits, manufacturers must be careful to test their products against the right product standard to be sure that the products are safe.

Electrical shock hazards can be prevented by the following types of tests:

A hipot test measures the ability of a product to withstand a high voltage applied between the circuits of a product and ground. An insulation resistance test measures the quality of the electrical insulation used in a product. A leakage current test checks that the current that flows between AC source and ground does not exceed a safe limit. A ground continuity test checks that a path exists between all exposed conductive metal surfaces and the power system ground. Each of these tests is described in detail later in this guide.

Worldwide Regulatory Compliance

In the field of product safety and product safety standards, significant change has taken place in the last ten years. Emphasis has been placed on the worldwide harmonization of product safety standards with the hope of establishing truly uniform global specifications. Although more progress needs to be made, results to date have been encouraging. Standards today are more closely coordinated than ever before. Manufacturers need to know and understand the safety standards that apply to their particular products. It is equally important for them to have a full grasp of the whole field of product safety regulation.

In an attempt to provide a basic explanation of the regulatory process, how it works, and why you must comply, let’s look at three of the major marketplaces, the United States, Canada, and the European Union (EU).

United States

In the U.S., regulatory requirements and federal laws are found in the Code of Federal Regulations. In this Code (CFR21-1910, Subpart S), you will find regulations for product safety approvals of electrical devices. The mandatory federal requirements specify that all electrical appliances and devices be “listed” by a Nationally Recognized Testing Laboratory (NRTL) for the purpose in which they will be used. The term “listed” means controlled, monitored, and otherwise placed under formal surveillance by the approval agency or testing laboratory. The term “NRTL” now applies to many laboratories operating under OSHA (Occupational Safety and Health Administration) accreditation for the purpose of carrying out product safety approvals according to accepted standards. For a current list of leading NRTLs, click here.

A listed product is commonly identified by the testing laboratory’s listing mark (UL, ETL, MET, FM, etc.) conspicuously attached to the product. This listing mark indicates that the device manufacturer has submitted a sample to the laboratory for product safety test and evaluation in accordance with the relevant product safety
standard. Once the NRTL finds the product fully complies with the standard, it grants the manufacturer permission to affix the agency listing label to the products. In the U.S., product safety certifications are generally carried out in accordance with the UL or IEC standards. As hundreds of standards exist, it is highly likely that at least one of these safety standards applies to your product.

Canada

Canadian requirements parallel those of the United States. Enforcement of the Canadian regulations is primarily the responsibility of the hydroelectric authority inspectors and/or customs officials within each province. Electrical products are considered compliant if they bear the certification mark from a testing laboratory which has obtained accreditation as a Certification Organization, and if the certification was performed in accordance with the Canadian National Standards, commonly called the “CSA” standards. A laboratory obtains status as a Certification Organization by passing an examination conducted by the Standards Council of Canada (SCC). The SCC is similar to, but not identical with, OSHA in the United States.

Within the Canadian system, a Certification Organization or “CO” is viewed in a manner similar to that of an NRTL within the U.S. system. Presently, several laboratories have obtained the status of both a U.S. NRTL as well as a Canadian CO. Therefore, you can, in many cases, obtain both a U.S. Listing and Canadian Certification from one laboratory. As in the U.S., factory surveillance and production line testing are also required steps in the approval process.

Europe

The European Community (EC) was established to create an overall economic environment conducive to economic growth. A key mechanism for doing so was to establish community- wide standards for product safety. This resulted in the issuance of the Low-Voltage Directive 73/23/EEC and the EMC Directive 89/336/EEC.

The EMC Directive 89/336/EEC defines the requirements for handling electromagnetic disturbances created by a device as well as similar disturbances which could affect proper operation of the device. It also deals with tests such as ESD and emissions.

The Low Voltage Directive provides the framework and procedures for determining the product safety compliance of a wide variety of electrical devices and covers dielectric, ground continuity, and numerous other safety tests. The main focus of this reference guide is the Low Voltage Directive which was adopted in 1973 and with which most electrical products designed for sale in the EC (European Community) must comply.

Before the adoption of the Low-Voltage Directive, products had to be tested in accordance with the appropriate standard for each country and by an approved test laboratory for that country. Having to meet all of these and national standards adversely affected manufacturers who wanted to market products in Europe because of the expense of testing to the various standards without significantly improving product safety. The Low Voltage and EMC directives are official legislation of the European Union and, as such, supersede any existing national regulations. Member countries within the EU must adopt and enforce the directives.

The Low Voltage directive does not specifically state which electrical tests are required for compliance, but instead indicates that products being sold in the EC must be constructed according to good engineering principles and should provide adequate safety so as to not endanger the user of the product. In addition, it states that appropriate standards for the product being tested must continue to be followed and that it is the responsibility of the European Union to periodically select so-called harmonized standards. The harmonized standards are typically IEC standards or standards published by the European Committee for Electrotechnical Standardization (CENELEC) which may actually be derived from IEC standards. Table 1 shows some of the more common harmonized standards.

Table 1: Harmonized Standards for European Union Countries

Standard

Description

EN 50091

Un-interruptible Power System (UPS)

EN 50144

Safety of Hand-Held Electric Motor Operated Tools

EN 60034

Rotating Electrical Machines

EN 60065

Household Electronic Equipment

EN 60204

Safety of Machinery

EN 60335

Household Appliances

EN 60950

Safety of Information Technology Equipment including Electrical Business Equipment

If a harmonized standard does not exist for the specific product being tested, the IEC or CENELEC standard covering that product is presumed to apply. If there is no IEC or CENELEC standard that covers the product, the national standards from the individual countries would apply, such as BEAB Document 40. Manufacturers can, if they wish, test their products to various national standards in addition to testing the products to the applicable harmonized standard.

An example of one such harmonized standard is BS EN 61010-1: 1993 Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory Use, Part 1: General Requirements. This standard published by CENELEC, is derived from IEC 1010-1, and specifies both design and routine production tests. The design tests are performed on a sample of products during initial design. Results from these tests must be available in a file for inspection. In addition to testing during the initial design phase, routine production tests are also required. The production tests, which are typically a subset of the design tests, usually include dielectric strength (hipot) and ground bond or ground continuity tests.

If the product passes all required tests, the Declaration of Conformity is completed and the product can be CE marked or labeled to show proof of compliance with the Low Voltage Directive. The Declaration of Conformity is normally a one page document that details the applicable directives and standards used to ensure full compliance. The Declaration must be completed before the CE marking can be applied. It must include the manufacturer’s name, full address, model numbers, product identification, applicable electrical ratings, full details of technical standards used to perform the evaluation, and the signature of an authorized representative of the company.